10W-30, 15W-40, 20W-50. We're sure you've seen these ... but that it follows the viscosity curve of a 10-weight oil when cold and behaves like a 30-weight oil when at operating temperature.

For example, a common oil rating is 15W-40, with 15 representing the oil's ... so thick that it affects engine efficiency. Correct Oil Weight Is Dependent On The Diesel Engine There is no catch ...